send a query message to a known node and the node re-send a response(I mean I explicitly contact a node by sending a message to ask him somethings).

if there is a DHT which contains information about nodes and their resources(each recording contain a key that represent IP @ of each node, and a list of its available resources), so if I have an access to this DHT (may be I am a member) and I know the key or the identifier of a given node, first can I look directly at the recording of this node without need to send it a message or a query(I mean I implicitly contact it)?second, if yes how? I mean how the DHT is represented physically, and how a node updates its information?

1 Answer
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In case 1. if you are sure the remote node has the resource, then DHT is useless.

In case 2, DHT helps you locate resources. Yes, you can take a look at the DHT record (if you have any) about the remote node. It will give you an indication of whether the resource might be available on that remote node.

Typically, DHT are in memory tables, or table stored on a local small database. There are many ways to push the info to remote nodes, a common way is push the info to random nodes.